Nature Astronomy\u202fpaper<\/a>, researchers\u202fat the University of Victoria\u2019s (UVic) Astronomy Research Centre\u202f(ARC)\u202fand the University of Minnesota\u202fsolved the problem.\u202f <\/p>\nThe answer? Stellar rotation.\u202f\u202f <\/p>\n
\u201cUsing high-resolution 3D simulations, we were able to identify the impact that the rotation of these stars was having on the ability for elements to cross the barrier,\u201d says Simon Blouin, lead researcher and postdoctoral fellow at UVic. \u201cStellar rotation is crucial and\u202fprovides a natural explanation for the observed chemical signatures in typical red giants. This discovery\u202fis another step forward in understanding how stars evolve.\u201d\u202f\u202f <\/p>\n
Scientists have long known that after Sun-like stars exhaust their core hydrogen, they expand into red giants up to 100 times their original size. Since the 1970s, scientists have\u202fobserved\u202fchanges to the surface composition of these stars during expansion, including a decline in carbon-12 to carbon-13 ratios. These compositional changes can only be explained by the transport of material from the nuclear-burning interior to the surface, but until now, researchers have been unable to prove how that transport happens.\u202f <\/p>\n
We knew that internal waves, generated by\u202fchurning motions in the convective envelope, were able to pass through this barrier layer, but previous simulations found that these waves transported very little material. We were able to show that\u202fthe rotation of the star\u202fdramatically amplifies how effectively these waves can mix material across the barrier, to an extent that matches the observed changes in surface composition.\u201d\u202f <\/p>\n
\u2014Simon Blouin, UVic postdoctoral fellow<\/p>\n
Blouin and his team found that mixing rates in the star studied can exceed those in non-rotating stars by over 100 times, and the rate increases with faster rotation rates.\u202fRed giants\u202frepresent\u202fa later evolutionary phase that our own Sun will eventually reach, making this research relevant to understanding the Sun\u2019s future. <\/p>\n
The\u202fimportant role\u202fof supercomputers\u202f <\/p>\n
To make this discovery, the researchers conducted hydrodynamical simulations\u2014large 3-dimensional simulations that represent\u202fhow the materials in stars move. These are\u202fvery large\u202fcalculations that require the most advanced supercomputers, and this finding was only possible now due to new computing resources.\u202f<\/p>\n
\u201cUntil recently, while stellar rotation was\u202fthought to be part of solving this\u202fconundrum, limited computing abilities prevented us from quantitatively\u202ftesting\u202fthe hypothesis,\u201d says Falk Herwig, principal investigator and\u202fdirector of ARC. \u201cThese simulations\u202fallow us to\u202ftease out small effects to determine what actually happens,\u202fhelping us to understand our observations.\u201d \u202f<\/p>\n
The team used\u202fcomputing resources at the\u202fTexas Advanced Computing Centre at the\u202fUniversity of Texas at Austin and\u202fthe new\u202fTrillium\u202fsupercomputing cluster at\u202fSciNet\u202fat the University of Toronto to conduct their simulations. Trillium, which\u202flaunched in August 2025, is one of the most powerful supercomputers\u202ffor large-parallel simulations\u202favailable for academic research in Canada and is one of several national supercomputers within the Digital Research Alliance of Canada.\u202fIts expanded computing power was key to completing this research. <\/p>\n
We were able to discover a new stellar mixing process only because of the immense computing power of the new Trillium machine. These are the computationally most intensive stellar convection and internal gravity wave simulations\u202fperformed to date.\u201d\u202f <\/p>\n
\u2014Falk Herwig, professor of physics and astronomy and director of ARC<\/p>\n
The computational techniques used to simulate stellar convection apply broadly to understanding flows in the natural world\u2014from ocean currents to atmospheric dynamics to blood flow. Herwig is\u202falso\u202fworking with researchers across these fields to develop shared approaches and infrastructure for large-scale flow simulations.\u202f\u202f <\/p>\n
Blouin plans to continue investigating stellar rotation. While this research studied one\u202fparticular\u202ftype of\u202fstar, he is interested in exploring what happens in other stars, including how different rotation profiles affect how efficiently the star mixes, and whether rotation also enhances wave mixing in other types of stars and evolutionary phases.\u202f\u202f <\/p>\n
This research was supported by the Natural Sciences and Engineering Research Council (NSERC), the National Science Foundation (NSF)\u202fand the US Department of Energy.\u202f\u202f <\/p>\n
\u202f <\/p>\n
Read the\u202fResearch Briefing<\/a>\u202fin\u202fNature\u202fAstronomy\u202f <\/p>\n","protected":false},"excerpt":{"rendered":"Advances in supercomputing have made solving a long-standing astronomical conundrum possible:\u202fHow\u202fcan we explain the changes in the chemical…\n","protected":false},"author":2,"featured_media":484615,"comment_status":"","ping_status":"","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[7],"tags":[800,195442,49,48,66],"class_list":["post-484614","post","type-post","status-publish","format-standard","has-post-thumbnail","category-science","tag-astronomy","tag-astronomy-research-centre","tag-ca","tag-canada","tag-science"],"_links":{"self":[{"href":"https:\/\/www.newsbeep.com\/ca\/wp-json\/wp\/v2\/posts\/484614","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.newsbeep.com\/ca\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.newsbeep.com\/ca\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.newsbeep.com\/ca\/wp-json\/wp\/v2\/users\/2"}],"replies":[{"embeddable":true,"href":"https:\/\/www.newsbeep.com\/ca\/wp-json\/wp\/v2\/comments?post=484614"}],"version-history":[{"count":0,"href":"https:\/\/www.newsbeep.com\/ca\/wp-json\/wp\/v2\/posts\/484614\/revisions"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/www.newsbeep.com\/ca\/wp-json\/wp\/v2\/media\/484615"}],"wp:attachment":[{"href":"https:\/\/www.newsbeep.com\/ca\/wp-json\/wp\/v2\/media?parent=484614"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.newsbeep.com\/ca\/wp-json\/wp\/v2\/categories?post=484614"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.newsbeep.com\/ca\/wp-json\/wp\/v2\/tags?post=484614"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}